The present invention refers to a tracking analog-to-digital converter, in particular of the differential input type.
A differential input tracking analog-to-digital converter comprises a differential amplifier to which the input terminals are applied. The output of the differential amplifier is placed in input to a comparator whose output is applied to the input of a back and forth counter (or up-down). The output of the back and forth counter, that corresponds to the output of the analog-to-digital converter, is applied to the input of a digital-to-analog converter. The output of the digital-to-analog converter is connected to the other input of the comparator.
The comparator compares the signal at the output of the differential amplifier with the signal at the output of the digital-to-analog converter, and its output commands the back and forth counter. If for example the value of the signal at the output of the differential amplifier is greater than the value of the output of the digital-to-analog converter, the counter continues increasing until the signal coming from the digital-to-analog converter exceeds that of the differential amplifier. At this point the output signal of the comparator changes value and the counter decreases its value. Consequently, the signal at the output of the digital-to-analog converter again returns higher than the signal at the output of the differential amplifier, therefore the counter increases its value and continues to oscillate around its input value until the input signal varies.
In view of the state of the technique described, an object of the present invention is to provide for a tracking analog-to-digital converter, in particular of the differential input type, which is easier to produce and has a reduced number of circuit elements.
In accordance with the present invention, these and other objects are reached by means of a tracking analog-to-digital converter, having a differential analog input including a first analog input and a second analog input, and a digital output with a first number of bits comprising: a back and forth counter having a direction input and an output, with a second number of bits; a digital-to-analog converter having a data input coupled to said output of said converter, a reference input and an output, with a second number of bits; a first comparator having a positive input, a negative input coupled to said output of said digital-to-analog converter and an output coupled to said direction input; characterized in that said reference input is coupled to said first analog input and said positive input of said first comparator is coupled to said second analog input.
These objects are also reached by means of a tracking analog-to-digital converter, having a differential analog input including a first analog input and a second analog input, and a digital output with a first number of bits comprising: a back and forth counter having a direction input and an output, with a second number of bits; a digital-to-analog converter having a data input coupled to said output of said converter, a reference input and an output, with a second number of bits; a first comparator having a positive input, a negative input coupled to said output of said digital-to-analog converter and an output coupled to said direction input; characterized in that said first analog input and said second analog input are coupled to the inputs of a second comparator that produces in output a signal corresponding to the sign of the signal of said differential analog input; said first analog input and said second analog input are selectively coupled to said positive input of said first comparator and selectively coupled on the contrary to said reference input.
These objects are further reached through a method for carrying out an analog-digital conversion of a differential signal by means of a tracking converter comprising a comparator coupled to a back and forth counter and a digital-to-analog converter that takes the output signal of said counter and couples it to an input of said comparator, characterized in that the difference of said differential input signal is carried out by the combination of said comparator and said digital-to-analog converter.